Following on success in a murine model system, a human IgE specific immunotoxin will be synthesized and evaluated for efficacy against an IgE- secreting human myeloma cell line. Monoclonal anti-human IgE antibody will be covalently attached to a variety of cytotoxins to produce a human IgE specific immunotoxin. This reagent will be tested for specific cytotoxicity against the human IgE myeloma line in vitro. The in vitro selected immunotoxin formulation will be evaluated in vivo by establishing the myeloma line in nu/nu mice and attempting to modulate serum human IgE levels by parenteral administration of immunotoxin. The ultimate goal of this research is to provide improved allergy therapy via IgE specific immunotoxins.